答复: [PERFORM] About “context-switching issue on Xeon” test case ？

Thank you for you reply!

“one of the indicators of that is that context switches per second will start to jump up and the machine gets

Sluggish”

--> Here is my database server indicator:

These is ther VMSTAT log of my database server as below:

2010-04-07 04:03:15 procs memory swap io system cpu

2010-04-07 04:03:15 r b swpd free buff cache si so bi bo in cs us sy id wa

2010-04-07 14:04:27 3 0 0 2361272 272684 3096148 0 0 3 1445 973 14230 7 8 84 0

2010-04-07 14:05:27 2 0 0 2361092 272684 3096220 0 0 3 1804 1029 31852 8 10 81 1

2010-04-07 14:06:27 1 0 0 2362236 272684 3096564 0 0 3 1865 1135 19689 9 9 81 0

2010-04-07 14:07:27 1 0 0 2348400 272720 3101836 0 0 3 1582 1182 149461 15 17 67 0

2010-04-07 14:08:27 3 0 0 2392028 272840 3107600 0 0 3 3093 1275 203196 24 23 53 1

2010-04-07 14:09:27 3 1 0 2386224 272916 3107960 0 0 3 2486 1331 193299 26 22 52 0

2010-04-07 14:10:27 34 0 0 2332320 272980 3107944 0 0 3 1692 1082 214309 24 22 54 0

2010-04-07 14:11:27 1 0 0 2407432 273028 3108092 0 0 6 2770 1540 76643 29 13 57 1

2010-04-07 14:12:27 9 0 0 2358968 273104 3108388 0 0 7 2639 1466 10603 22 6 72 1

My postgres version: 8.1.3;

My OS version: Linux version 2.4.21-47.Elsmp((Red Hat Linux 3.2.3-54)

My CPU:

processor : 7

vendor_id : GenuineIntel

cpu family : 15

model : 6

model name : Intel(R) Xeon(TM) CPU 3.40GHz

stepping : 8

cpu MHz : 3400.262

cache size : 1024 KB

physical id : 1

I donnt know what make the “context-switching” storm ？

How should I investigate <javascript:;> the real reason ?

Could you please give me some advice ?

Thank you !

-----邮件原件-----
发件人: Scott Marlowe [mailto:scott(dot)marlowe(at)gmail(dot)com]
发送时间: 2010年4月10日 13:05
收件人: Greg Smith
抄送: RD黄永卫; pgsql-performance(at)postgresql(dot)org
主题: Re: [PERFORM] About “context-switching issue on Xeon” test case ？

2010/4/9 Greg Smith <greg(at)2ndquadrant(dot)com>:

> RD黄永卫 wrote:

>>

>> Anybody have the test case of “ context-switching issue on Xeon” from

>> Tm lane ？

>>

>

> That takes me back:

> http://archives.postgresql.org/pgsql-performance/2004-04/msg00280.php

>

> That's a problem seen on 2004 era Xeon processors, and with PostgreSQL

> 7.4. I doubt it has much relevance nowadays, given a) that whole area of

> the code was rewritten for PostgreSQL 8.1, and b) today's Xeons are

> nothing like 2004's Xeons.

It's important to appreciate that all improvements in scalability for

xeons, opterons, and everything else has mostly just moved further

along to the right on the graph where you start doing more context

switching than work, and the performance falls off. The same way that

(sometimes) throwing more cores at a problem can help. For most

office sized pgsql servers there's still a real possibility of having

a machine getting slammed and one of the indicators of that is that

context switches per second will start to jump up and the machine gets

sluggish.

For 2 sockets Intel rules the roost. I'd imagine AMD's much faster

bus architecture for >2 sockets would make them the winner, but I

haven't had a system like that to test, either Intel or AMD.